<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>兄弟节点</title>
	</head>
	<body>
		<div class="yeye">
			<div class="fuqin">
				<div class="erzi">
					<span>1</span>
					<span>2</span> 
					<span>3</span>
					<span>4</span>
				</div>
			</div>
		</div>
		<script>
			var erzi = document.querySelector('.erzi');
			var firstErzi = erzi.firstElementChild;
			console.log(firstErzi);
			console.log(firstErzi.nextElementSibling);
			console.log(firstErzi.nextElementSibling.nextElementSibling);
			console.log(firstErzi.nextElementSibling.nextElementSibling.previousElementSibling);
		</script>
	</body>
</html>